1. Field of the Invention
The present invention relates to systems and methods for protecting vehicle occupants from injury. More specifically, the present invention relates to a compact tethering system for maintaining the position of a cushion of an airbag system, such as an inflatable curtain designed to protect vehicle occupants against lateral impact.
2. Description of Related Art
The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the explosion of pressurized gas from an inflator. Expanding gases from the inflator fill the airbags, which immediately inflate to protect the driver and/or a passenger from impact against the windshield, dashboard, and steering wheel.
Side impact airbags have also been developed in response to the need for protection from impact against the side of the vehicle (also known as lateral impact). These airbags, which are commonly referred to as “inflatable cushions” or “inflatable curtains,” may be mounted in the vehicle over the doors, and may inflate during an accident to cover the windows, doors, and lateral surfaces of the vehicle. The inflatable cushion may also be connected to tethers that extend from the ends of the airbag to anchoring points within the vehicle. These tethers may exert tension on the inflated cushions to keep the cushions generally between the occupant and the lateral surface of the vehicle.
However, tether systems known in the art have a number of disadvantages. First of all, many known tether systems require that the tether be extended longitudinally away from both ends of the inflatable cushion. Consequently, the front tether must be extended from the front end of the inflatable cushion toward the front of the vehicle and the rear tether must be extended from the rear end of the inflatable cushion toward the rear of the vehicle. Such a design is incompatible with most trucks and sport utility vehicles (“SUVs”) in which the passenger compartment of the vehicle ends abruptly behind a lateral surface over which it would be desirable to position a cushion. In these vehicles, there is typically insufficient space for tether extension rearward from the edge of the inflatable cushion. Accordingly, most known tethering systems cannot be used.
One of the main purposes in attaching a tethering system to an inflatable cushion is to protect the occupant by applying tension to the inflatable cushion to keep the inflatable cushion in the proper position. Without such tension, there is an inherent risk that the inflatable cushion will improperly inflate and injure the occupant. Additionally, during rollover conditions, if the inflatable cushion is not secured in the proper position via tethers, the motion of the occupant may force the inflatable cushion out of an open window, thereby eliminating any possible safety benefits of the inflatable cushion.
Additionally, many known inflatable cushions and tethering systems provide insufficient tension to prevent occupant excursion. “Occupant excursion” occurs when all or part of the vehicle occupant is extended or ejected from the vehicle, usually through an open door or window, during an accident. Obviously, occupant excursion can be very dangerous, especially during rollover conditions. However, since many known tethering systems permit the airbag cushion to move far enough to expose the window and door of the vehicle, these systems may not provide sufficient protection against occupant excursion.
Similarly, “bag slap” may occur when the cushion inflates inward of the window or door to strike an occupant. Many known tethering systems provide inadequate protection against bag slap.
Accordingly, a need exists for a tethering system suitable for use in vehicles that do not have sufficient interior space behind the inflatable cushion to extend a rear tether. Furthermore, a need exists for such a tethering system that tensions the cushion tightly enough to keep the cushion in place during inflation and impact of an occupant against the cushion. Such a tethering system should be cost effective to manufacture and install.